Eighty-six mixed-parity Large White sows were used to determinethe effect of diets with reduced CP content or supplementedwith essential AA on 28-d lactation performance under humidtropical climatic conditions. This experiment was conductedin Guadeloupe (West French Indies, latitude 16°N, longitude61°W) between February 2007 and January 2008. Two seasonswere distinguished a posteriori from climatic measurement variablescontinuously recorded in the farrowing room. The average minimumand maximum ambient temperatures and average daily relativehumidity for the warm season were 20.5 and 28.2°C, and 93.8%,respectively. The corresponding values for the hot season were22.7 and 29.4°C, and 93.7%, respectively. The dietary experimentaltreatments were a normal protein diet (NP), a low protein diet(LP), and a NP diet (NP+) supplemented with essential AA. TheNP and LP diets supplied the same levels of standardized digestibleLys (i.e., 0.80 g/MJ of NE), and the NP+ diet supplied 0.95g/MJ of NE. No interaction between season and diet compositionwas noted on any response variable evaluated. The ADFI was decreased(P < 0.05) in the hot season (i.e., 3.69 vs. 4.72 kg) andtherefore decreased by 500 g per °C increase of ambienttemperature under high relative humidity conditions. The ADFItended to be greater with the LP and NP+ diets when comparedwith the NP treatment (i.e., +10%, P = 0.08). Litter BW gainand mean BW of piglets at weaning were greater (P < 0.05)during the warm season than during the hot season (2.3 vs. 1.8kg/d and 7.5 vs. 7.1 kg, respectively). Milk production andcomposition were not affected by dietary treatments but wereaffected by season (8.1 vs. 6.8 kg/d, for warm and hot seasons,respectively; P < 0.01). The sows fed LP and NP+ diets tendedto have decreased backfat thickness losses (3.3 and 3.8 mm,respectively; P > 0.08). In conclusion, the hot season inhumid tropical climates, which combines high levels of temperatureand humidity, has a pronounced negative impact on performanceof lactating sows. Diets with low CP content or supplementedwith essential AA can attenuate the effects of hot and humidseason by increasing ADFI in lactating sows.